Abstract: In a pneumatic motor that includes a vaned rotor, a rotor chamber having a gas inlet and gas outlet means, a housing and an axially extending rotor shaft to rotate in said chamber, structure to control and muffle the escape of exhaust gas comprisingA. a first exhaust chamber extending about the rotor chamber and into which pressurized exhaust gas escapes from the rotor chamber,B. a second exhaust chamber spaced axially from the first exhaust chamber and extending about the shaft, and primary porting communicating between the first and second exhaust chambers, andC. a third exhaust chamber extending about the shaft and located radially inwardly of the second exhaust chamber, there being radially inwardly extending porting spaced about the shaft and communicating between the second and third exhaust chambers to direct escaping exhaust directionally inwardly and in conflicting turbulent streams to dissipate energy contained in said streams.